This invention relates to high pressure piston seals and more particularly to a high pressure piston seal with low pressure sealing capability.
It is known to seal dynamic pistons with standard O-rings to provide sealing, however, friction and wear are typically less than desired. Energized cap seals are used to prevent wear, but unless lightly loaded, do not significantly reduce friction. Teflon seals sacrifice low pressure (0-100 psi) sealing to provide high pressure (2000-4000 psi) sealing.
U.S. Pat. No. 4,101,140 provides a seal ring with finely grooved sealing surfaces which are roll-formed on the ring, and responses to force entrained fluid from the grooves.
U.S. Pat. No. 4,566,703 seal arrangement has multi-lobes intended to retain lubrication without being pressure responsive.
U.S. Pat. No. 4,235,447 provides a metallic seal with annular ridges intended for internal combustion engines.
U.S. Pat. No, 3,727,925 shows a cap type seal arrangement designed to deal with reversing pressure direction without pressure responsiveness.
U.S. Pat. No, 3,494,624 provides a seal designed to lubricate a dry shaft and reduce heat build-up without being pressure responsive.
U.S. Pat. No. 3,418,001 illustrates a seal design to prevent seal failure due to twisting, scrubbing or spiraling without pressure responsiveness.
U.S. Pat. No. 3,268,235 shows a seal design with machined grooves without being pressure responsive.
U.S. Pat. No. 2,968,501 is a seal design for pressure reversal and reduced wear without pressure responsiveness.
The foregoing and most known devices use the same seal "foot print" at all pressures from low to high. Some seals have grooves which are machined in their sealing surface to provide a labyrinth effect, but are costly to produce. Shortcomings are typically high loading and high friction for low pressure sealing, or low loading and low pressure leakage for low friction high pressure sealing.
Accordingly, the problem of high pressure piston sealing with low pressure sealing is accomplished according to the invention.